Impact modified styrene polymers are well known in the plastics industry. Dispersion of particulate rubber tougheners throughout the resin matrix, enhance the impact strength of the styrene polymers. Typically, improvements in impact strength are obtained by incorporating ever increasing amounts of particulate rubber toughening agents. However, the resulting increases in impact strength is accompanied by a decrease in both tensile strength and surface gloss.
The polymer blends of the current invention provide materials with improved impact strength and surface gloss while maintaining reasonable tensile strength.
It is known in the art that some physical properties of styrenic or acrylic type polymers may be improved by alloying them with one or more additional polymers. In some cases, the resulting mixture can have improved mechanical properties, such as improved impact strength or toughness.
Chemical Abstracts 109: 171278v [Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1988, 29(2), 180-1] discloses that physical blends of block SBR (styrene content: 75.2 weight %) and a copolymer of methyl methacrylate and styrene are partially compatible. The morphological and mechanical properties of the blend are strongly dependent on tile molding/mixing process used to produce the blend. The SBR could only be toughened when the ideal morphology of the blend was obtained.
Chemical Abstracts 106: 85901z [JP 61/200, 151] discloses thermoplastic compositions comprising from 5 to 95 weight % of a block copolymer and from 95 to 5 weight % of a thermoplastic polymer (e.g. ABS). The block copolymer is derived from coupling an aromatic vinyl polymer block with an aromatic vinyl monomer-conjugated diene copolymer block. The subject thermoplastic compositions apparently have improved impact strength.
Chemical Abstracts 112: 8285y [JP 61/291,610] discloses the use of "impact modifiers" for thermoplastic polymers. The modifiers are basically similar to the block copolymer disclosed by Chemical Abstracts 106:85901z.
Chemical Abstracts 99: 196070j [JP 58/122,954] discloses improvement of anisotropy of a styrene hydrocarbon-conjugated diene block copolymer by blending it with a styrene-methacrylic ester copolymer. Such a blend, when extruded to form a molded plate, apparently possesses superior physical properties.
Chemical Abstracts 111: 8522c [JP 01/45614] discloses high-impact styrene polymer compositions comprises a major amount of a styrene (50 to 90 weight % )-conjugated diene (50 to 10 weight %) block copolymer and a minor amount of a styrene-based polymer (e.g. styrene-methyl methacrylate copolymer).
It would be desirable to have a composition which possesses a combination of improved properties, including improved impact strength while retaining gloss.